Optimal design of diamond-air microcavities for quantum networks using an analytical approach

Abstract

Defect centres in diamond are promising building blocks for quantum networks thanks to a long-lived spin state and bright spin-photon interface. However, their low fraction of emission into a desired optical mode limits the entangling success probability. The key to overcoming this is through Purcell enhancement of the emission. Open Fabry-Perot cavities with an embedded diamond membrane allow for such enhancement while retaining good emitter properties. To guide the focus for design improvements it is essential to understand the influence of different types of losses and geometry choices. In particular, in the design of these cavities a high Purcell factor has to be weighed against cavity stability and efficient outcoupling. To be able to make these trade-offs we develop analytic descriptions of such hybrid diamond-and-air cavities as an extension to previous numeric methods. The insights provided by this analysis yield an effective tool to find the optimal design parameters for a diamond-air cavity.

Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities

“…The full cavity mode-structure must be modeled including all the interferences [11]. Conceptually, the cavity modes can be described using a coupled-cavity approach [6,19,43]. In this picture, there are two cavity modes, one defined by the air-gap bounded by the top DBR and the diamondair interface; the other is defined by the diamond-air interface and the bottom DBR layer (Fig.…”

Cryogenic platform for coupling color centers in diamond membranes to a fiber-based microcavity

“…The additional losses of (2100 ± 600)ppm per round trip can be attributed to the diamond membrane. We conjecture the surface roughness of rms = (3.6 ± 0.2) nm as main reason, which would explain additional scattering losses L sc of up to 11,700 ppm depending on the diamond thickness and hence the position of the diamond boundary with respect to the cavity mode standing wave field, estimated using an extended transfer matrix model with partially reflective rough interfaces [43].…”

“…The ZPL linewidth also shows the expected cubic dependence (red) [50]. Due to the vanishing doublet peak structure at 150 K, no linewidth value was extracted at this temperature the cavity mode and the effective cavity length L eff , which factors in the diamond membrane and the penetration of the light field into the dielectric mirror stacks, weighted by the local energy density of the light field mode [43]. We perform time-correlated single-photon counting after pulsed excitation of the SiV − ensemble to investigate the influence of the cavity on the excited-state lifetime of the emitters.…”

“…Introducing a thin layer of diamond into an optical resonator alters the cavity properties. First, both the surface roughness of the diamond membrane as well as dirt on this surface can lead to additional loss channels of the cavity, potentially reducing the finesse depending on the thickness of the membrane layer [43]. The transmission of the mirror with the diamond layer attached can be significantly enlarged depending on the thickness of the diamond layer, as it can have a similar effect as an anti-reflective coating layer [44].…”

“…We fit the data with a model following Eqs. 1 and 2, where Q eff is experimentally determined, w 0 and L eff are calculated by a coupled Gaussian beams model and the transfer matrix model [43,44], is calculated from the electrical field at the implantation depth given by the SRIM simulation, and 0 and QE are free parameters. The measured data are shown in Fig.…”